1. Field of the Invention
The present invention relates to a process for preparing an optical article having a layer with a variable index of refraction involving transferring a coating or a stack of coatings from a carrier to at least one geometrically defined surface of the substrate of said optical article. The process can be implemented in a short period of time without any risk of deformation of the substrate.
The invention also relates to a coated carrier for use in the above process.
2. Description of Related Art
It is a common practice in the art to coat at least one main surface of a lens substrate, such as an ophthalmic lens or lens blank, with several coatings for imparting to the finished lens additional or improved optical or mechanical properties. These coatings are designated in general as functional coatings.
Thus, it is usual practice to coat at least one main surface of a lens substrate, typically made of an organic glass material, with successively, starting from the surface of the lens substrate, an impact-resistant coating (impact resistant primer), an abrasion- and/or scratch-resistant coating (hard coat), an anti-reflection coating and, optionally, an anti-fouling top coat. Other coatings, such as a polarized, photochromic or dyeing coating may also be applied onto one or both surfaces of the lens substrate.
Numerous processes and methods have been proposed for coating a surface of optical articles. U.S. Pat. No. 6,562,466 and U.S. Pat. Appl. Nos. 2005/0140033 and 2005/250870 describe a process for transferring or applying coatings from at least one support or mold part onto at least a geometrically defined surface of a lens blank comprising:                providing a lens blank having at least one geometrically defined surface;        providing a support or mold part having an internal surface bearing a coating and an external surface;        depositing onto said geometrically defined surface of said lens blank or onto said coating a pre-measured amount of a curable adhesive composition;        moving relatively to each other the lens blank and the support to either bring the coating into contact with the curable adhesive composition or bring the curable adhesive composition into contact with the geometrically defined surface of the lens blank;        applying a sufficient pressure onto the external surface of the support so that the thickness of a final adhesive layer once the curable composition cured is less than 100 micrometers;        curing the layer of adhesive composition; and        withdrawing the support or mold part to recover the lens blank with the coating adhered onto the geometrically defined surface of said lens blank.        
U.S. Pat. No. 6,562,466 and U.S. Pat. Appl. Nos. 2005/0140033 and 2005/250870 use a liquid light- or thermally-curable adhesive composition during the transfer of the coating layers from the carrier to the surface of the lens substrate. The liquid curable adhesive composition is required to stick both to the exposed coating on the carrier and the geometrically defined surface of the lens substrate. The total thickness of the transferred coating layers is typically less than 50 μm.
Currently, there seems no fast and low cost way to realize patterned ophthalmic articles designed and optimized to the patient's individual requirements, and more generally, optical articles.
Optical articles generally have a homogeneous refractive index. A refractive index profile in an optical material offers an additional degree of freedom with regard to the use of the article. Actually, the refractive index profile allows the optical path of the rays to be varied independently of the geometry of the article.
The manufacturing methods described in the prior art for creating specific functional lenses having refractive index profiles are very costly due to the amount of time and expertise required.
U.S. Pat. No. 6,712,466, WO 2004/034095, WO 2004/015481 and WO 2004/106990, all to Ophtonix, Inc., describe an optical article called “wavefront aberrator,” which uses a variable index layer. It includes a cavity that is sandwiched between a pair of transparent plates or windows, typically lenses. The cavity is filled with one or more monomers, or pre-polymers, monomer mixtures and polymerization initiators. This polymerizable resin composition exhibits an index of refraction change as it polymerizes, and the change can be controlled by the extent of its polymerization degree, or curing. The refractive index of the composition may be controlled as a function of position across and through the composition layer, so as to create a predetermined three-dimensional refractive index profile.
However, the above described invention has a lot of drawbacks in the real practice and is also not cost effective, since all the lenses or semi-finished lenses to be stored are required to be provided with a variable index coating layer during the lens manufacture. A problem may come out with mass production or patients' specific requirements for lens substrates. It is hard to cover all the lens materials including polarized or photochromic lens materials.
Consequently, a need exists for a low cost and easy process for preparing patterned optical articles.